The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 410
Fig. 374.—Joint in Cast-Iron Ducts (Scale \) with lead 2| inches diameter and 4 feet long must be drawnthrough the duct, and each is required to hold an air pressureof 5 lbs. per square inch for 30 minutes when closed at the ends.Split Pipes.—These are used when only one or two ductsare being laid… … Fig. 375.—Right-Angle Split Pipe tion of the ducts altered. They are pipes made in two halveslongitudinally, fitted together to form one pipe by means ofsquare pins passed through holes in flanges formed on theedges, as shown in Fig. 375 ; the joints are clamped by taperedcotters passing through…
Telephone
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